1. Field of the Invention
The invention relates to an inkjet printer adopting a station type ink supply system in which a main tank and a sub-tank are capable of being connected to, and disconnected from, each other. The main tank and the sub-tank are connected to each other when ink is supplied from the main tank to the sub-tank.
2. Description of Related Art
In a printhead of an inkjet printer, a droplet of liquid, such as ink, is ejected from a nozzle by a piezoelectric element when the piezoelectric element deforms. The droplet of liquid may also be ejected from the nozzle by a heat-generating resister when that heat generating element volumetrically changes an air bubble. Usually, the nozzle is not provided with a valve. Rather, a meniscus is formed in the nozzle in a concave manner inwardly from the nozzle surface so that no ink leaks from the nozzle when the printhead is in a stand-by mode.
The nozzle is a small opening. Accordingly, liquid in the nozzle forms a dome-shaped meniscus therein due to surface tension. The meniscus is concave when the pressure inside the nozzle is less than the atmospheric pressure. Such a meniscus prevents the liquid from leaking from the nozzle when the printhead is in stand-by mode.
Japanese Laid-Open Patent Application No. 2004-181952 discloses an inkjet printer adopting a station type ink supply system in which an ink absorber made of a porous member is disposed in a sub-tank which is mounted on a printhead. The ink absorber absorbs ink due to capillary action, thereby decreasing the pressure in the sub-tank. In this way, the pressure in the sub-tank is made to be less than the atmospheric pressure, thereby ensuring that a meniscus is formed in each nozzle of the printhead.
The porous member may be a formed or sponge member having a number of open cells (spaces). The porous member may also be a member made of interlaced fibers that create a number of open cells (spaces).
Ink is supplied from the main tank to the sub-tank via an ink supply path. When an ink absorber is disposed in this ink path, the ink absorber may create a great resistance to the flow of ink through the ink path. Accordingly, ink cannot be quickly supplied from the main tank to the sub-tank.
In view of the forgoing problem, it is an object of the invention to provide an inkjet printer adopting a station type ink supply system in which ink is quickly supplied from a main tank to a sub-tank while maintaining a meniscus in each nozzle of a printhead when the printhead is in stand-by mode.